Waterflood completion system and assembly

ABSTRACT

A waterflood completion system usable in a well includes a mandrel disposed on a tubing string deployable down a borehole. The mandrel has a side pocket with one or more ports for communicating the tubing string with an annulus of the borehole A waterflood regulator arrangement is connected to the mandrel and has at least one screen directly included therein spaced from the mandrel and lying adjacent the tubing string.

CROSS REFERENCE TO RELATED APPLICATION

This application relates to and claims priority from U.S. ProvisionalApplication Ser. No. 61/253,983, filed Oct. 22, 2009, which is fullyincorporated herein by reference.

FIELD

The present disclosure generally relates to downhole oilwell technology,and more particularly, pertains to waterflood side pocket mandrelinstallations, such as used in injector wells.

BACKGROUND

Only a portion of oil can be recovered from a permeable oil-bearingsubterranean formation as a result of the natural pressure of thereservoir. So called secondary recovery techniques are thus used toforce the oil out of the reservoir. The simplest method of expelling oilof the reservoir formation is by direct replacement with another fluid,typically water or gas.

Waterflooding is one of the most successful and extensively usedsecondary recovery methods. As depicted in FIG. 1, water is injectedunder pressure into the reservoir R via an injector well IW driving theoil through the reservoir into a production well PW. In this manner,wells that have finished primary production can continue to produce oilthereby extending the economic life of the well field, and increasingthe total recovered oil from the reservoir.

In a typical waterflood completion system, the injector well has acasing that passes through the reservoir. A tubing string positioned inthe casing is provided with a number of side pocket mandrels which aretypically located between packers. Surrounding the tubing string, thesepackers separate the annulus (the space between the tubing string andthe casing) into multiple isolated zones in communication with thereservoir that can be separately treated. Particular to the waterfloodapplication, each side pocket mandrel is installed with a waterfloodregulating device that enables precision subsurface control. Waterinjected through the tubing string enters a waterflood regulator valve,passes through an orifice and exits through a port into a zone to beflooded.

Waterflood applications provide a metered flow rate of water into thereservoir. The injected water aids in maintaining the injector wellstatic bottomhole pressure, and washes the oil production through theformation from the injector well to the production well significantlyincreasing a recoverable reserve of the reservoir. The design of theside pocket mandrel allows for retrieval and placement of flow controldevices by the use of wireline, slickline and other deployment methodsthat will allow for changing the flow characteristics of the waterfloodregulator valve and matching the required injection rates to optimizeproduction of the reservoir. Using packers to isolate separate zones ina single injector well, the waterflood completion system is designed sothat each zone receives the appropriate rates of injected water.

Known waterflood side pocket mandrels are similar in that they are partof the tubing string that utilizes a snorkel or flow tube to inject thewater at a regular rate from the tubing string into the annulus. Thesnorkel is currently designed as a short length of pipe that connectsfrom an outlet on the mandrel using a threaded connection to a standardseparate check valve which prevents backflow from the reservoir. Watercontrolled and delivered at the surface of the well exits from theregulator valve into the annulus, passes through perforations in thecasing and interacts with the surrounding reservoir. In some cases,sandscreens are located at the injector zones and are controlledseparately from the tubing string in an attempt to prevent introductionof backflow particulates from the reservoir into the side pocketmandrel. In other designs, sliding sleeves are required to controlinjection rates into the individual zones to provide a continuousinjection rate. In the past, it has been customary to utilize more thanone tubing string to effect the desired secondary oil recovery.

SUMMARY

The present inventors have found that the prior art waterfloodcompletion systems as described above have number of drawbacks which canlimit the efficiency of secondary oil recovery. Accordingly, the presentdisclosure provides solutions which improve upon waterflood regulatorarrangements installed in side pocket mandrels by adapting the mandrelsdirectly to the sandscreens, integrating the check valve into theregulator arrangement and eliminating the slickline operations foradjustment to the regulator valve and the requirement for slidingsleeves in the tubing string. The present disclosure furthercontemplates compensating for variations in the particular mandrel andregulator arrangement, easing installation cost and complexity andremoving the need for surface control of the water flow.

In one example, a waterflood completion system usable in a well includesa mandrel disposed on a tubing string deployable down a borehole. Themandrel has a side pocket with one or more ports for communicating thetubing string with an annulus of the borehole. A waterflood regulatorarrangement is connected to the mandrel and has at least one screendirectly included therein spaced from the mandrel and lying adjacent thetubing string.

The regulator arrangement defines at least one flow path for regulatingflow of fluid into the mandrel through the regulator arrangement and outof the screen into the annulus. The regulator arrangement typicallyincludes a regulator valve installed in the side pocket, a flow tubeconnected to the mandrel and a support structure operatively connectedbetween the flow tube and the tubing string for supporting the screen.The support structure includes an adapter connected to the flow tube,and a shroud attached to the tubing string and supporting the screen.The screen is positioned between the adapter and the shroud. The supportstructure includes a connector joined to the screen and retained by theshroud. A check valve is incorporated within the flow tube, and the flowtube is made adjustable in length. The present disclosure alsocontemplates the regulator arrangement defining a first flow path fordelivering fluid to a first screen located beneath the mandrel, and asecond flow path for delivering fluid to a second screen located abovethe mandrel.

In another example, a waterflood regulator arrangement usable in a wellcasing and adapted to regulate fluid flow between a tubing string and anannulus of a borehole includes a regulator valve adapted to be installedin a side pocket mandrel of the tubing string. A flow tube is positionedin communication with the regulator valve and is adapted to be securedto the mandrel. A support structure is operatively connected to at leastthe flow tube and supports a screen.

In a further example, a waterflood completion system usable in a wellincludes a mandrel disposed on a tubing string deployable down aborehole, the mandrel having at least one side pocket with one or moreports for communicating the tubing string with an annulus of theborehole. At least one regulator valve is installed in the side pocketof the mandrel for regulating flow between the mandrel and the annulus.At least one adapter is spaced from the mandrel and surrounds the tubingstring. At least one flow tube connects the mandrel and the adapter. Atleast one shroud is attached to the tubing string, and at least onescreen is coupled to the shroud. Fluid delivered from the tubing stringinto the mandrel is regulated by the valve and flows through the flowtube into the adapter and out the screen relative to at least one sideof the mandrel for delivery into the annulus.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view of a cross section of a reservoir positionedbetween an injector well and a production well;

FIG. 2 is a schematic diagram of the injector well provided with awaterflood completion system according to the present disclosure;

FIG. 3 is an enlarged fragmentary sectional view of one example of awaterflood regulator arrangement used in FIG. 2;

FIG. 4 is an enlarged detail view of a flow tube of the waterfloodregulator arrangement shown in a retracted position;

FIG. 5 is a view similar to FIG. 4 showing the flow tube in an extendedposition;

FIG. 6 is an enlarged detail view of an adapter, a shroud and a screenof the waterflood regulator arrangement taken on line 6-6 of FIG. 3; and

FIGS. 7 and 8 are fragmentary sectional views of another example of awaterflood regulator arrangement.

DETAILED DESCRIPTION

In the following description, certain terms have been used for brevity,clearance and understanding. No unnecessary limitations are to beimplied therefrom beyond the requirement of prior art because such termsare used for descriptive purposes and are intended to be broadlyconstrued. The different configurations and methods described herein maybe used alone or in combination with other configurations, systems andmethods. It is to be expected that various equivalents, alternatives andmodifications are possible within the scope of the appended claims.

Referring now to the drawings, FIG. 2 illustrates a waterfloodcompletion system 10 for an injector well 12 used in secondary oilrecovery and having a casing 14 that passes through a reservoirformation 16 containing residual oil. A tubing string 18 positionedinside the casing 14 is provided with a series of spaced apart sidepocket mandrels 20 which are located between packers 22. Each mandrel 20is in communication with the tubing string 18 and an annulus 24extending between the tubing string 18 and the casing 14. The packers 22surround the tubing string 18 and separate the annulus 24 into multipleisolated zones that can be separately treated. Installed in each mandrel20 is a waterflood regulator arrangement 26 which functions to regulatefluid (e.g. water or the like), such as delivered into the tubing string18 by a pump at the surface of well 12, between the tubing string 18 andthe annulus 24. Once in the annulus 24, fluid can then pass throughperforations 28 formed in the casing 14 at each zone, and interact withthe surrounding formation 16 to forcibly sweep residual oil therefrominto an adjacent production well.

FIGS. 3-6 show one example of waterflood regulator arrangement 26comprised of a waterflood regulator valve 30, an elongated, adjustableflow tube or snorkel 32, a tubular adapter 34 and tubular shroud 36 witha surrounding cylindrical sandscreen 38. Each waterflood regulatorarrangement 26 used in the completion system 10 is designed to operateindependently of one another, and separately controls the volume offluid that can enter the isolated zone adjacent the formation 16 to betreated. In this way, each of the waterflood regulator arrangements 26can compensate for differential pressure changes and provide a constantvolume of fluid for each zone.

As seen in FIG. 3, the tubing string 18 has an inner wall 40 with aconstant diameter that defines a flow passageway for transporting fluidto each mandrel 20 and waterflood regulator arrangement 26 installedrelative thereto. The inner wall 40 is formed with inlet ports 42 whichare in communication with inlets on the waterflood regulator valve 30installed directly within the mandrel 20. As is known, water injectedinto the tubing string 18 via inlet ports 42 typically enters a filterin the regulator valve 30, passes through a fixed orifice in a stem andflows from an outlet aligned with an exit port 44 formed in the mandrel20. If the differential pressure through the regulator valve 30increases or decreases, the position of the stem changes. This regulatesfluid flow through the outlet of the valve 30 while maintaining aconstant flow rate independent of pressure variations.

With further reference to FIGS. 4 and 5, the flow tube or snorkel 32 hasa flow path defined by a central passageway 46 in communication with aflow chamber 48, an annular passageway 50 and an outlet 52. A portion ofthe central passageway 46 is formed in an inner member 54 which isthreadably adjustable relative to an outer sleeve 56. The outer sleeve56 is fixed to an intermediate section 58 that is joined to a checkvalve housing assembly 60 that is provided with a check valve 62 fornormally preventing backflow from the annulus 24 into the mandrel 20.The check valve 62 has a valve member 64 normally biased by a spring 66against a valve seat 68 formed on the intermediate section 58. Knurledrings 70, 72 and 74 are provided to facilitate selective adjustment ofthe inner member 54 relative to the outer sleeve 56, intermediatesection 58 and check valve housing 60 so that the snorkel 32 may bevaried in length (e.g. ±0.5 inches) to compensate for variations inmanufacturing the remaining elements of the mandrel 20 and the regulatorarrangement 26. A locking ring 76 is provided on the outer sleeve 56 toenable locking the snorkel 32 in either a retracted position shown inFIG. 4 or an extended position shown in FIG. 5. The snorkel 32 isconnected to the mandrel 20 by means of an end 78 of the inner member 54which is threadably secured in the mandrel outlet port 44. As seen bestin FIG. 3, the snorkel 32 extends externally of the mandrel 20 along anouter surface of the tubing string 18.

Referring to FIG. 6, the adapter 34 surrounds the tubing string 18 andis connected to the snorkel 32 by means of an end 80 of the check valvehousing 60 which is threadably received in an inlet 82 on the adapter34. Outlet 52 of the snorkel 32 is in communication with an annularchamber 84 formed in the adapter 34. Inner portions 86 of the adapter 34are in sealed relationship with the external surface of the tubingstring 18. The outer diameter of the adapter 34 is substantially equalto the outer diameter of the mandrel 20.

The shroud 36 is a non-perforated, solid tube having an end 88 which isthreadably coupled at 90 to a lower end 92 of the tubing string 18. Theshroud 36 defines a channel 94 for retaining a connector 96 that isattached to the perforated sandscreen 38 by a number of torque bolts 98.A sandscreen 38 has one solid portion 100 which extends between theadapter 34 and shroud 36, and another solid portion 102 which runsbetween the external surface of the tubing string 18 and a sealingsurface 104 on the adapter 34. A number of set screws 106 on the adapter34 helps maintain the desired spacing of the sandscreen 38. The innerdiameter of the shroud 36 is substantially equal to the inner diameterof the tubing string 18.

With the waterflood completion of FIG. 2 having the regulatorarrangement 26 installed, well operators can proceed with a waterfloodoperation by injecting fluid (e.g. water or the like) into the tubingstring 18. As depicted by the arrows A in FIGS. 3 and 6, the injectedfluid passing down the tubing string 18 enters inlet ports 42, theregulator valve 30 and the central passageway 46 of the snorkel 32. Whenthe pressure of the fluid has reached a predetermined value, the valvemember 64 opens against the bias of spring 66 and allows the fluid toflow from the flow chamber 48 through the annular passageway 50 andoutlet 52 into the adapter chamber 84. The fluid then flows betweenportion 102 and an external surface of tubing string 18, and between theportion 100 and the shroud end 88 and flows out of a perforated portion108 of sandscreen 38 into the annulus 24 and through the casingperforations 28 to the formation 16. Thus, it should be appreciated thatfluid is injected along a flow path through the snorkel 32, the adapter34, the shroud 36 and the sandscreen 38 which are all convenientlylocated beneath the mandrel 20 in a substantially inline arrangementadjacent the tubing string 18.

FIGS. 7 and 8 illustrate another example of a water regulatorarrangement 26′ which modifies the waterflood regulator arrangement 26described above to include a manifold 110 in the adapter 34. Themanifold 110 defines a pathway 112 in communication with the chamber 84in adapter 34. An elongated tubular side pipe 114 in communication withthe pathway 112 is connected between the adapter 34 positioned beneaththe mandrel 20 and an adapter 34′ positioned above the mandrel 20. Anopen end of the adapter 34′ is sealed with a plug 116. A shroud 36′ isconnected to an upper end 118 of tubing string 18 and carries asandscreen 38′. In this example, one flow path will enable injection offluid into the sandscreen 38 as described above, while another flow pathdefined by the pathway 112 and the side pipe 114 will enablesimultaneous injection of fluid into a pathway 120 of adapter 34′ sothat fluid is also delivered to the sandscreen 38′ above the mandrel 20.

In a further example, two waterflood regulator arrangements areinstalled in two side pockets of a mandrel. One flow path will enableinjection of fluid into an adapter and a sandscreen beneath the mandrel,while another flow path defined by a feed tube connected betweenadapters located above and below the mandrel will again enablesimultaneous injection of fluid into a sandscreen above the mandrel.This example is similar to, but more efficient than that shown in FIGS.7 and 8 as the inlet ports of the two regulator valves are independentlyflooded with fluid.

The present disclosure thus provides a waterflood completion system inwhich side pocket mandrels may be adapted directly to sandscreens thatprevent the backflow of particulates from the formation into themandrels. The present design has been found to ease installation andreduce cost and complexity of running the completion as only onecompletion string needs to be installed, instead of two as has been donein the past. In the present completion system, the check valve isintegrally designed in the snorkel so that there is no need toexternally install the check valve. In multi-zone applications, thecheck valve operates to prevent reverse flow of fluid back into thetubing string so as to stop any contamination. The present designfurther eliminates the need for surface control of the flow as thewaterflood regulator valves adjust automatically to pressure ratefluctuations and meter the flow along at least one flow path asrequired. Traditional sliding sleeves used in the tubing string andscreens separately run and landed at the injection zones are eliminated,and there is no need for slickline operations to replace or adjust thewaterflood regulator valves because the fluid flow is continuouslyregulated.

What is claimed is:
 1. A waterflood completion system usable in a wellcomprising: a mandrel disposed on a tubing string deployable within aborehole, the mandrel having a side pocket with one or more ports forcommunicating the tubing string with an annulus of the borehole; and awaterflood regulator arrangement connected to the mandrel and having atleast one screen directly included therein spaced from the mandrel andlying adjacent the tubing string.
 2. The system of claim 1, wherein theregulator arrangement defines at least one flow path for regulating flowof fluid into the mandrel through the regulator arrangement and out ofthe screen into the annulus.
 3. The system of claim 1, wherein theregulator arrangement includes: a regulator valve installed in the sidepocket; a flow tube connected to the mandrel; and a support structureoperatively connected between the flow tube and the tubing string forsupporting the screen.
 4. The system of claim 3, wherein the supportstructure includes an adapter connected to the flow tube, and a shroudattached to the tubing string and supporting the screen.
 5. The systemof claim 4, wherein the screen is positioned between the adapter and theshroud.
 6. The system of claim 4, wherein the support structure includesa connector joined to the screen and retained by the shroud.
 7. Thesystem of claim 3, wherein a check valve is incorporated within the flowtube.
 8. The system of claim 3, wherein the flow tube is adjustable inlength.
 9. The system of claim 1, wherein the regulator arrangementdefines a first flow path for delivering fluid to a first screen locatedbeneath the mandrel, and a second flow path for delivering fluid to asecond screen located above the mandrel.
 10. A waterflood regulatorarrangement usable in a well casing and adapted to regulate fluid flowbetween a tubing string and an annulus of a borehole, the arrangementcomprising: a regulator valve adapted to be installed in a side pocketmandrel of the tubing string; a flow tube positioned in communicationwith the regulator valve and adapted to be secured to the mandrel; and asupport structure operatively connected to at least the flow tube andsupporting a screen.
 11. The arrangement of claim 10, wherein a checkvalve is incorporated within the flow tube.
 12. The arrangement of claim10, wherein the flow tube is adjustable in length.
 13. The arrangementof claim 10, wherein the support structure includes: an adapterconnected to the flow tube, and a shroud adapted to be joined to thetubing string and directly supporting the screen.
 14. A waterfloodcompletion system usable in a well comprising: a mandrel disposed on atubing string deployable down a borehole, the mandrel having at leastone side pocket with one or more ports for communicating the tubingstring with an annulus of the borehole; at least one regulator valveinstalled in the side pocket of the mandrel for regulating fluid flowbetween the mandrel and the annulus; at least one adapter spaced fromthe mandrel and surrounding the tubing string; at least one flow tubeconnecting the mandrel and the adapter; at least one shroud attached tothe tubing string; and at least one screen coupled to the shroud,whereby fluid delivered by the tubing string into the mandrel isregulated by the valve and flows through the flow tube into the adapterand out the screen relative to at least one side of the mandrel fordelivery into the annulus.
 15. The system of claim 14, wherein theadapter has a flow chamber which is in communication with the flow tube.16. The system of claim 14, wherein the flow tube has an inner memberwhich is threadably connected relative to the outer sleeve so that theflow tube is adjustable between a retracted position and an extendedposition.
 17. The system of claim 14, wherein an inner diameter of theshroud is equal to an inner diameter to the tubing string.
 18. Thesystem of claim 14, wherein the screen is positioned between the adapterand the shroud.
 19. The system of claim 14, wherein the screen extendsbeyond the adapter.
 20. The system of claim 14, wherein a portion of thefluid flow to the adapter is delivered to another adapter and flows outof another screen relative to an opposite side of the mandrel.